With its Simple Storage Service and Elastic Compute Cloud, Amazon is blazing a trail to Web services and mixing it up with the likes of IBM and Sun — and maybe even Microsoft and Google.

Here’s a pop quiz:

Which of the following does Amazon want to sell you?

A. The book Eat, Pray, Love by Elizabeth Gilbert

B. A Nintendo Wii

C. An Apple Mac laptop

D. One terabyte of storage

E. The computing power of 10,000 servers

F. Thought processes of a million human brains

G. All of the above

If you chose “all of the above,” there’s a strong chance you’re one of the more than 330,000 customers—predominantly developers and startups—tapping Amazon.com’s vast computer network to take advantage of some of the world’s most inexpensive computing power and data storage.

With the launch of the Simple Storage Service (S3) in March 2006 and the Elastic Compute Cloud (EC2) in August 2006, the $14.8 billion e-commerce giant served notice on the IBMs, Microsofts, Googles and Sun Microsystems of the world: Amazon wants a piece of the action.

“It’s really a new line of business for us, these Web services that are measured and metered very much like a water bill or a phone bill,” adds AWS lead evangelist Jeff Barr.

By stepping beyond its circumscribed sphere of selling books, toys, music, DVDs and computers online, Amazon is not just poaching far from its own turf by penetrating an entirely new market, it’s also challenging the established players in the emerging software as a service (SaaS), managed services and grid-computing sectors. It’s as if General Motors suddenly opened up its factories worldwide to allow thousands of companies to make their products using its equipment and facilities.

“This definitely is a disruptive technology,” says James Staton, an analyst at Forrester Research. “It’s totally different from the mainstream offerings today. It’s something that can be used without anyone’s authority, where you can pay with a credit card. For a high-tech startup, for, say, two guys in a garage, it means they can start and grow a $100 million business without ever having bought a server.”

Doug Bartholomew is a career journalist who has covered information technology for more than 15 years. A former senior editor at IndustryWeek and InformationWeek, his freelance features have appeared in New York magazine and the Los Angeles Times Magazine. He has a B.S. in Journalism from Northwestern University.